Abstract:

In the field of digital image watermarking, watermarking algorithms mainly focus on gray images, whereas most of color images watermarking algorithms usually embed watermarking only in the luminance component or in each channel of color image separately. These algorithms are unable to make full use of the redundant space of color images, thus affecting the watermarking’s transparency and robustness. To solve these problems,we propose a novel color image watermarking algorithm based on the three-dimensional discrete cosine transform (3DDCT) and the singular value decomposition (SVD). Firstly, the watermarking image is pre-processed and the color image is subdivided to nonoverlapping blocks.Secondly, we perform the 3DDCT for each block and apply the SVD in the first component of the 3D-DCT coefficients. We use the quantization method and the relationship method to embed watermarking in the largest singular value and the second component of 3D-DCT coefficients respectively at the embedding watermarking stage.At the watermarking extraction stage, we extract the watermarking image using the quantization method and the relationship method separately and the results are compared. The result with higher correlation value is chosen as the final extracted watermarking. Experimental results show that the proposed algorithm has good transparency and the ability to resist common signal processing and fuzzy, distorted, sharpening attacks.Key words:

Key words: color image watermarking;three-dimensional discrete cosine transform;singular value de-composition;relationship;quantization;robustness